The present invention relates to a release device for a safety actuator. It more specifically relates to the release of a safety actuator and to safety actuators making it possible to initiate a protective action in a nuclear reactor.
For example, it is known that a nuclear reactor comprises a large number of devices making it possible to control its operation. These devices are called safety actuators. In the case of an accident or incident, these actuators can be released extremely rapidly in such a way that their protective action can stop the incident. In nuclear reactors, the values of a certain number of physical quantities, such as the pressure, temperature, neutron flux, etc are measured at a certain number of points. The values of these quantities are then compared with reference values in various devices. These devices normally supply logic comparison signals with a non-zero value, when the values of the physical quantities are within a predetermined value range, corresponding to the normal operation of the reactor. When the physical quantities pass outside this safety range, the devices supply logic output signals, e.g. with zero values. It is the output signals of these devices which are applied to the safety actuator release devices. In certain cases, these release devices are of the logic 2/2 type making it possible to initiate an emergency action by a signal supplied at an output, said signal being e.g. of logic state 1, when two of its inputs receive control signals, whose logic state is 0. These control signals come from the aforementioned devices.
Safety actuator release devices are known, which comprise release means constituted e.g. by a reversed output OR gate, two of the inputs of this gate being respectively connected to the outputs of two AND gates having two inputs. Each of these gates receives at one of their control inputs, a control signal coming from the aforementioned devices, whilst another input can receive a test signal making it possible to impose at the output of the OR gate, a signal with a predetermined logic state 1, no matter what the logic state of the control signals applied to each of the control inputs of the two AND gates.
The main disadvantage of the known devices is that they can only control low power actuators. However, in many fields and particularly in nuclear reactors, the safety actuators require a relatively high power level, which cannot be obtained by means of logic circuits integrated onto a semiconductor substrate.